The invention relates to an air desiccating apparatus with a tank which is filled with a preferably granular desiccator substance which adsorbs moisture, which is thermally insulated relative to its surroundings and which exhibits inlet orifices and outlet orifices, and with a heater element arranged in the tank, by means whereof the desiccator substance can be regenerated by heating and evaporation. The thermal insulation of the tank serves to permit the desiccator substance to be heated more uniformly during the regeneration process, and to economise energy. The operating temperature during the regeneration process is approximately 180.degree..
No such apparatus, the tank of which is simply surrounded by a layer of thermal insulation material, can be traced. However, a corresponding apparatus for desiccating the process air of an ozone generator is known from German Offenlegungsschrift No. 2,937,070, published Apr. 2, 1981. This apparatus has the special feature that the steam expelled from the desiccator substance during the regeneration process can be fully condensed and the condensate collected in a liquid tank. For this purpose the tank filled with the desiccator substance is enveloped by a metal bell, which is in turn surrounded by a housing open at the bottom and at the top. Clear interstices are present between the tank, the bell and the housing respectively, so that this arrangement, including the air cushions, has an overall thermal insulation effect.
It has now been discovered that the thermal insulation of the tank which is desired in the regeneration phase is disadvantageous when the apparatus is erected in a warm room at approximately 25.degree. or higher, particularly if a high air humidity prevails. Heat is evolved during the adsorption of the moisture on the desiccator substance during the desiccation process, namely the more so as the air to be desiccated is more humid. At a correspondingly high room temperature, as mentioned, localization of heat therefore occurs with such high temperatures in the desiccator substance that an equilibrium state results between accumulated water molecules and those released again, so that the desiccating apparatus becomes ineffective.